1. Field of the Invention
The present invention relates to a rotary handpiece for endodontic files used to clean and enlarge root canals of teeth.
2. Description of the Prior Art
Endodontics is the branch of dentistry which involves the treatment of pulp through root canal therapy. Such therapy generally involves the cleaning of the root canal to remove damaged tissue therefrom and to enlarge the root canal so that it can be filled with an inert sealing material, e.g., gutta-percha. Typically, a dentist will drill into the upper part of the tooth to locate the root canal and thereafter clean and enlarge the root canal using small endodontic instruments, generally referred to in the art as "files."
The cleaning and enlarging of a root canal is complicated by the fact that the root canal is not only very small but often follows a curved path. Accordingly, the file must be very thin and flexible in order to enter the root canal and follow its path. Also, the file must have a sufficient strength so that it is not easily broken off within the root canal.
Heretofore, the most common procedure followed by dentists in performing root canals has been to utilize hand manipulated endodontic files of progressively increasing size. A particularly effective such endodontic file is known as a K-type file which includes a tapered shaft having a conical point and three or four spiral cutting edges along the length of the tapered portion of the shaft. When a K-type file is manipulated by hand to clean and enlarge a root canal, a number of types of cutting strokes can be utilized which generally fall into the categories of filing or reaming. A filing stroke utilizes axial reciprocation of the cutting instrument along the length of the root canal without rotating the instrument. Thus, the edges of a K-type instrument cut the interior walls of the root canal when a filing stroke is used therewith. A reaming stroke refers to the use of rotational motion established by rotating the instrument about its longitudinal axis. While there are various kinds of instruments, some of which cut in a single rotational direction, K-type files have spiral cutting edges which are rotationally bi-directional in that they may cut when rotated either clockwise or counterclockwise. The spiral cutting edges are generally right handed whereby when a K-type file is rotated clockwise, it tends to thread itself into the root canal like a wood screw. Thus, the dentist must be careful not to penetrate too deeply into the root canal as a result of self-threading which can damage the tooth and subject the file to excessive loading whereby it sticks or breaks off in the canal.
A variety of dental instrument drive devices, known in the art as "handpieces", have been developed for rotating dental instruments. While the use of rotary handpiece driven endodontic files has achieved some degree of success, a continuing problem involves the self threading of the endodontic instrument into the canal whereby the instrument progresses into the canal too rapidly and becomes excessively loaded. Such excessive stress on the instrument driven by a handpiece can result in sticking or breaking of the instrument in the canal, a condition which is difficult to correct.
Thus, there is a need for an improved rotary handpiece for cleaning and enlarging a root canal of a tooth with a rotary endodontic file which prevents the file from becoming excessively loaded due to self threading and the problems which result therefrom.